German patent application DE 10 2015 105 702.6 filed on Apr. 14, 2015 shows a bus system, particularly for use in industrial automation, having a supply module and at least one load module that are connected via a four-wire data line and a DC power supply.
In the supply module and in the load module of the bus system, a respective combination of inductive and capacitive assemblies is used in order to apply two DC-isolated DC voltages to the four-wire data line. Using just a single cable that consists of the four-wire data line, it is thus possible for two DC-isolated direct currents in addition to two differential data signals to be transmitted in parallel on the two wire pairs of the data line. The functionality of the bus system is not altered, which means that any bus structures such as a star, line or ring are possible.
Copper-based data transmission methods are always restricted in their extent because the damping of the lines is always greater than zero in realistic environments. This means that the signal amplitude is lowered ever further as line length increases, and, upward of a defined length, is no longer distinguishable from noise. In the case of Ethernet, the maximum length of the lines is specified at 100 m, greater distances not being able to be spanned by this means.